[PATCH] device-mapper multipath: Avoid possible suspension deadlock
To avoid deadlock when suspending a multipath device after all its paths have
failed, stop queueing any I/O that is about to fail *before* calling
freeze_bdev instead of after.
Instead of setting a multipath 'suspended' flag which would have to be reset
if an error occurs during the process, save the previous queueing state and
leave userspace to restore if it wishes.
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 5d40555..bb3ad79 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1055,14 +1055,17 @@
if (test_bit(DMF_BLOCK_IO, &md->flags))
goto out_read_unlock;
- error = __lock_fs(md);
- if (error)
- goto out_read_unlock;
-
map = dm_get_table(md);
if (map)
+ /* This does not get reverted if there's an error later. */
dm_table_presuspend_targets(map);
+ error = __lock_fs(md);
+ if (error) {
+ dm_table_put(map);
+ goto out_read_unlock;
+ }
+
up_read(&md->lock);
/*
@@ -1121,7 +1124,6 @@
return 0;
out_unfreeze:
- /* FIXME Undo dm_table_presuspend_targets */
__unlock_fs(md);
clear_bit(DMF_BLOCK_IO, &md->flags);
out_write_unlock: